The invention relates generally to the field of circuit interrupting devices. More particularly the invention relates to a technique for quenching an arc that results from interruption of a current carrying path between a source of electrical power and a load.
Various circuit interrupters are currently available and have been developed for interrupting a current carrying path between a source of electrical power and a load. These circuit interrupting devices may take the form of circuit breakers, contactors, relays, motor starters and the like. In general, such devices include one or more moveable contacts and associated one or more stationary contacts. The contacts are joined to complete a current carrying path through the device during normal operation. The contacts may be separated in response to desired events such as turning off a circuit breaker or de-energizing the coil voltage of a relay or contactor in addition to fault conditions such as current overload, thermal protection, or other undesired events. Upon separation of the contacts an electrical arc is generated which results in an increase in temperature and pressure inside the circuit interrupting device. It is desirable to dissipate, extinguish, or quench the arc quickly so as to prevent damage to the contacts of the circuit interrupting device, the device itself, or the load that is being protected.
There have been various approaches to improve extinguishing an arc in a circuit interrupter. These techniques include lengthening the arc column by increasing the separation of the contacts, constricting the arc so as to increase the pressure resulting in a decreased arc diameter, and introducing ferromagnetic plates which attract the arc and split it into smaller arcs. Additional benefit is gained by the introduction of materials that undergo surface ablation during the arc event which aid in the rapid expansion and extinguishing of the arc. While the various combinations of these techniques are useful in quenching an arc there is a need for further improvement in the containment of the arc pressure generated as a result of the circuit interruption event in order to dissipate an arc more quickly and efficiently